Variable displacement axial pump or motor

ABSTRACT

A variable displacement pump or motor unit having a power shaft drivingly connected to a rotor rotatably mounted in the stationary housing. Spherical pistons in an annular series are mounted on the rotor and each cooperates with a cylinder cup which has a sliding slipper base portion slidably engaging the stationary tilt plate. The tilt plate is pivotally mounted on the frame and the angle of the tilt plate with respect to the axis of the unit is adjusted for variable displacement.

United States Patent Clark [45] Mar. 14, 1972 [54] VARIABLE DISPLACEMENT AXIAL PUMP OR MOTOR [72] Inventor: William B. Clark, Indianapolis, Ind.

[73] Assignee: General Motors Corporation, Detroit,

Mich.

[221 Filed: July 6, 1970 [21] Appl. N0.: 52,632

[51] int. Cl ..F0lb13/04 [58] Field ofSearch ..417/460, 462; 91/490,488, 91/503-507 56] References Cited UNITED STATES PATENTS 3,274,946 9/1966 Simmons ..91/490 3,320,902 5/1967 Paschke.... .....417/460 1,710,567 4/1929 Carey ..91/503 2,141,945 12/1938 Tweedale... ..91/488 2,157,692 5/1939 Doe et a1. ..91/499 FOREIGN PATENTS OR APPLlCATlONS 656,487 l/l963 Canada ..91/499 1,161,762 l/l964 Germany.....

Primary Examiner-William L. Freeh AttorneyW. E. Finken and A. M. lHeiter [5 7] ABSTRACT A variable displacement pump or motor unit having a power shaft drivingly connected to a rotor rotatably mounted in the stationary housing. Spherical pistons in an annular series are mounted on the rotor and each cooperates with a cylinder cup which has a sliding slipper base portion slidably engaging the stationary tilt plate. The tilt plate is pivotally mounted on the frame and the angle of the tilt plate with respect to the axis of the unit is adjusted for variable displacement.

2 Claims, 2 Drawing Figures Patented Mmh M mm 3,648,567

INVENTOR.

BY d J/m. (702/8 A TTORNEV VARIABLE DISPLACEMENT AXIAL PUMP R MOTOR This invention relates to hydrostatic machines or pump or motor units and particularly to a variable displacement axial type pump or motor.

The invention provides a variable displacement pump or motor unit of the axial type which eliminates side hydraulic forces between the piston and cylinder and provides a hydraulic axial force coaxial with the axis of the cylinder so the load of the cylinder is perpendicular to the tilt plate.

The pump or motor unit has a plurality of spherical pistons mounted in an annular series about the perimeter of a rotor which is drivingly connected to the power shaft and rotatably mounted in the stationary housing. A cup shaped piston is mounted on each cylinder and has a sliding slipper bearing base seated on the stationary tilt plate. Since the spherical piston has circular line sealing contact with the cylindrical internal wall of the cylinder and the slipper bearing is perpendicular to the cylinder axis the fluid force is perpendicular to the tilt plate. The angle of the tilt plate is adjustable to vary the displacement. The inlet and outlet flow paths extend from the stationary housing and the ports at the interface between the thrust hearings on the stationary housing and on the rotor and through passages in the rotor extending through each of the pistons.

An object of the invention is to provide a variable displacement pump or motor unit of the axial type having an annular series of spherical pistons mounted on a drive rotor and a plurality of cup shaped cylinders reciprocally mounted on each piston and each having a sliding slipper base portion sliding on a stationary tilt plate.

Another object of the invention is to provide in a variable displacement pump or motor unit of the axial type a spherical piston and a cylindrical cup shaped cylinder with the pistons fixed in an annular series to a power rotor element and the cylinders having a sliding slipper base sliding on a stationary tilt plate so that the hydraulic pressure between the cylinder and piston does not produce any side loading of the cylinder against the piston and the cylinder is loaded perpendicularly and centrally against the tilt plate.

These and other objects of the invention will be more apparent from the following description and drawing of a preferred embodiment.

FIG. 1 diagrammatically shows a cross section of the variable displacement pump or motor unit of the axial type.

FIG. 2 is a section of FIG. I on line 2-2.

Referring to the drawing, the power shaft 10, which may be the input shaft in the pump or the output shaft in the motor, is rotatably mounted by suitable bearing means 11 in a portion of the stationary housing 12, having fluid inlet passage 14 and fluid outlet passage 15 respectively connected to the kidney shaped inlet port 16 and the kidney shaped outlet port 17 at the thrust bearing surface 18 on the stationary housing when the tilt plate 41 is tilted as shown and rotation is in the direction of arrow a. The rotor 21 is drivingly connected to the input shaft 10 and together provide the rotor means. The rotor 21 has an annular series of spherical pistons 22 fixedly mounted thereon by individual projections 23 which support the pistons on the rotor in spaced relation to provide clearance for the reciprocation of the cylinder 26 which is reciprocally mounted on the piston. Each piston has a spherical surface portion 27 cooperating with a cylindrical internal wall surface 28 of the cylinder. Each piston has a central passage 31 connected by an angled passage 32 through the extension 23 and body of rotor 21 to a piston port 33 at the thrust bearing surface 34 of the rotor. The piston ports 33 are located in an annular series about the machine axis at the same diameter as the inlet and outlet ports 16 and 17 for transfer of fluid at the interface between the thrust bearing surfaces on the rotor and housing.

The base portion 36 of the cylinder 26 has a fluid passage 37 therein to supply fluid under pressure to the slipper bearing recess 38 which hydrostatically supports the slipper bearing surface 39 on the tilt plate. The tilt plage 41 has an car 42 pivotally mounted on a support pin 43 suitably mounted by justs the angle of the tilt plate from a position perpendicular to the machines axis and providing no displacement to angular positions to vary displacement of the pump or motor unit.

When the unit operates as a pump, the power shaft 10 functions as an input shaft to rotate the rotor 21 and the pistons 22 which carry along the cylinders 26 which slide on their hydrostatic slipper bearings on the tilt plate 41. When the tilt plate is at an angle to the machine axis as shown, the cylinders reciprocate on the pistons and with rotation of the rotor in the direction of the arrow a, fluid will be pumped from the inlet to the outlet.

If fluid under pressure is supplied to the inlet 14, the unit operates as a motor and drives the power shaft 10 as an output shaft in the direction of arrow a.

During operation of this unit either as a pump or a motor, the variable volume chamber between the piston and cylinder is sealed at the contact line, a circle, between the spherical surface 27 of the piston 22 and the internal cylindrical wall surface 28 of the cylinder 26. The circular sealing line is always in a plane perpendicular to the longitudinal axis of the cup cylinder 26. Thus, there is no hydraulic unbalance between the piston and cylinder which would tend to increase the hydrostatic load on one side thereof. Thus, the hydrostatic load is coaxial with the cylinder axis. Also, since the hydrostatic bearing surface on the cylinder is perpendicular to the cylinder axis, the hydraulic force seating the cup cylinder base or its hydrostatic bearing against the tilt plate is always perpendicular to the tilt plate and centrally located with respect to the cylinder or on the longitudinal axis of the cylinder. Thus, the friction between the piston and cylinder is very low and the slipper bearing has uniform hydrostatic pressure around its perimeter. Since the cylinder is a lightweight struc ture, the centrifugal force urging the cylinders radially outward is small compared to the hydraulic forces and does not have a significant affect.

It will be appreciated that modifications may be made in the above described preferred embodiment of the invention.

It is claimed:

1. In a hydrostatic machine; a stationary housing having a rotary bearing on the machine axis and an axial thrust bearing face having an inlet, port and an outlet port transverse of the machine axis; rotor means having a rotor rotatably mounted in said rotary bearing for rotation about said machine axis and having means connectable for a drive, axial thrust bearing means, including a face on one end of said rotor, for engaging said thrust bearing face on said housing, a plurality of pistons fixed on said rotor and individually projecting axially from the other end of said rotor in a direction opposite said axial thrust bearing means and arranged in an annular series concentric with said machine axis and each having a spherical surface portion with the full diameter transverse of the machine axis and a passage extending through each piston and rotor to the thrust bearing face of the rotor means for alternate communication with said inlet and outlet ports; and annular bearing member mounted on said housing and positioned at an angle transverse to the machine axis and having a substantially flat bearing surface having an elliptical path facing toward said other end of said rotor; a cup shaped cylinder on each piston having a base and an internal cylindrical wall closed at one end by said base and having a circular line contact seal with the spherical surface portion of said piston to form an operating chamber within said cylindrical wall and between said piston and base of said cylinder for hydraulic fluid providing the hydraulic force at all times on the axis of the cylindrical wall and a base having fixed therewith a flat slipper bearing perpendicular to the cylinder wall axis in bearing engagement with and moving relative to said bearing surface in an elliptical path on said bearing surface to rotatably support said cylinders and said hydraulic force being perpendicular to said annular bearing surface.

2. In a hydrostatic machine; a stationary housing having a rotary bearing on the machine axis, an axial thrust bearing face having a semicircular inlet port and a semicircular outlet port located transversely of the machine axis and a support pivot coaxially located on the machine axis; rotor means having a rotor rotatably mounted in said rotary bearing for rotation about the machine axis having means connectable for a drive, axial thrust bearing means on one end of said rotor engaging said thrust bearing face on said housing, a plurality of pistons fixed on said rotor and individually projecting axially from the other end of said rotor and in a direction opposite said thrust bearing means arranged in an annular series concentric with said machine axis and each having a spherical surface portion with the full diameter transverse of the machine axis and a passage extending longitudinally through each piston and rotor to the thrust bearing face of the rotor means for alternate communication with said inlet and outlet ports; a

tilt plate nonrotatably pivotally mounted on said support pivot having an annular substantially flat bearing surface portion having a circular and elliptical path facing toward said other end of said rotor and adjustably positioned at a variable angle transverse to the machine axis; a cup shaped cylinder on each piston having a base and an internal cylindrical wall having circular line contact with the spherical surface of said piston forming an operating chamber in said cylindrical wall between said base of said cylinder and said piston providing the hydraulic force at all times on the axis of the cylindrical wall and said base having fixed therewith a flat hydrostatic slipper bearing perpendicular to the cylinder wall axis cooperating with said annular bearing surface to rotatably support said cylinders for relative movement in a circular and elliptical path and said hydraulic force being perpendicular to said annular bearing surface of said tilt plate. 

1. In a hydrostatic machine; a stationary housing having a rotary bearing on the machine axis and an axial thrust bearing face having an inlet port and an outlet port transverse of the machine axis; rotor means Having a rotor rotatably mounted in said rotary bearing for rotation about said machine axis and having means connectable for a drive, axial thrust bearing means, including a face on one end of said rotor, for engaging said thrust bearing face on said housing, a plurality of pistons fixed on said rotor and individually projecting axially from the other end of said rotor in a direction opposite said axial thrust bearing means and arranged in an annular series concentric with said machine axis and each having a spherical surface portion with the full diameter transverse of the machine axis and a passage extending through each piston and rotor to the thrust bearing face of the rotor means for alternate communication with said inlet and outlet ports; an annular bearing member mounted on said housing and positioned at an angle transverse to the machine axis and having a substantially flat bearing surface having an elliptical path facing toward said other end of said rotor; a cup shaped cylinder on each piston having a base and an internal cylindrical wall closed at one end by said base and having a circular line contact seal with the spherical surface portion of said piston to form an operating chamber within said cylindrical wall and between said piston and base of said cylinder for hydraulic fluid providing the hydraulic force at all times on the axis of the cylindrical wall and a base having fixed therewith a flat slipper bearing perpendicular to the cylinder wall axis in bearing engagement with and moving relative to said bearing surface in an elliptical path on said bearing surface to rotatably support said cylinders and said hydraulic force being perpendicular to said annular bearing surface.
 2. In a hydrostatic machine; a stationary housing having a rotary bearing on the machine axis, an axial thrust bearing face having a semi-circular inlet port and a semi-circular outlet port located transversely of the machine axis and a support pivot coaxially located on the machine axis; rotor means having a rotor rotatably mounted in said rotary bearing for rotation about the machine axis having means connectable for a drive, axial thrust bearing means on one end of said rotor engaging said thrust bearing face on said housing, a plurality of pistons fixed on said rotor and individually projecting axially from the other end of said rotor and in a direction opposite said thrust bearing means arranged in an annular series concentric with said machine axis and each having a spherical surface portion with the full diameter transverse of the machine axis and a passage extending longitudinally through each piston and rotor to the thrust bearing face of the rotor means for alternate communication with said inlet and outlet ports; a tilt plate nonrotatably pivotally mounted on said support pivot having an annular substantially flat bearing surface portion having a circular and elliptical path facing toward said other end of said rotor and adjustably positioned at a variable angle transverse to the machine axis; a cup shaped cylinder on each piston having a base and an internal cylindrical wall having circular line contact with the spherical surface of said piston forming an operating chamber in said cylindrical wall between said base of said cylinder and said piston providing the hydraulic force at all times on the axis of the cylindrical wall and said base having fixed therewith a flat hydrostatic slipper bearing perpendicular to the cylinder wall axis cooperating with said annular bearing surface to rotatably support said cylinders for relative movement in a circular and elliptical path and said hydraulic force being perpendicular to said annular bearing surface of said tilt plate. 